1. Field of the Invention
The invention relates to a fuel tank system with a fuel tank and a storage element, and to a method for monitoring a fuel tank system.
2. Related Art
Numerous measures have been introduced in recent decades for reducing the pollutant emissions of motor vehicles. One such measure consists in using a fuel tank system in which a fuel tank is connected to a storage element for the temporary storage of hydrocarbons. During the refueling of motor vehicles, hydrocarbons are outgassed from the fuel, and it is sought to prevent the hydrocarbons from passing into the atmosphere. Also, in the presence of high temperatures or when driving over uneven surfaces, increased outgassing of hydrocarbons from the fuel occurs, wherein it must be ensured, in an effective manner, that the hydrocarbons do not escape into the atmosphere. In particular, in the case of hybrid vehicles, in which the internal combustion engine is entirely shut down over long travelling distances, it is necessary for outgassed hydrocarbons to be temporarily stored in an effective manner in order to be burnt at a later point in time upon a restart of the internal combustion engine. For this purpose, fuel tank systems that consist of a fuel tank and a storage element for the temporary storage of hydrocarbons have become established, wherein the fuel tank and the storage element are connected to each other in such a manner that the hydrocarbons outgassed from a fuel situated in the fuel tank are stored in the storage element, wherein the storage element is connected to a first line through which fresh air can be delivered to the storage element, and the storage element is connected to a second line which connects the storage element to an intake line and through which fresh air enriched with hydrocarbons can be delivered from the storage element to the intake line. In this manner, the storage element can be cyclically purged with fresh air, and the stored hydrocarbons can be supplied to an intake line that connects the internal combustion engine to the air filter and supplies air for combustion to the internal combustion engine. It is thus possible for the hydrocarbons outgassed from the fuel tank to be burnt in the internal combustion engine, and an escape of the hydrocarbons into the atmosphere is reliably prevented. An example of a fuel tank system according to the prior art is found in the PCT application with the application number PCT/KR2011/006516. In order to ensure error-free operation of the fuel tank system, the sealing action of the entire fuel tank system has to be checked at regular intervals. This check of the sealing action cannot be limited to garage visits of the motor vehicle but rather the check of the sealing action has to be undertaken in the vehicle, i.e., onboard, throughout the driving operation of the motor vehicle.